Oral L-Citrulline Supplementation Attenuates Blood Pressure Response to Cold Pressor Test in Young Men

Abstract

Oral L-citrulline is efficiently converted to L-arginine, which has been shown to decrease brachial blood pressure (BP) at rest and during the cold pressor test (CPT). However, aortic BP may better reflect cardiovascular risk than brachial BP. The purpose of this study was to test the hypothesis that oral L-citrulline supplementation attenuates brachial BP and aortic hemodynamic responses to CPT. Brachial BP, aortic BP, stroke volume (SV), and wave reflection at rest and during CPT were evaluated in 17 young (21.6 +/- 0.9 years) normotensive men. Subjects were randomly assigned to 4 weeks of oral L-citrulline (6 g/day) or placebo in a crossover design. Hemodynamic responses to CPT were reevaluated after each treatment. During CPT, there were significant (P < 0.05) increases in brachial and aortic BP [systolic (SBP), diastolic (DBP), and pulse pressure (PP)], augmentation index (AIx), SV, and a decrease in transit time of the reflected wave (Tr) from baseline. Compared to placebo, oral L-citrulline treatment decreased (P < 0.05) brachial SBP (-6 +/- 11 mm Hg), aortic SBP (-4 +/- 10 mm Hg), and aortic PP (-3 +/- 6 mm Hg) during CPT but not at rest. There was an inverse correlation (r = -0.40, P < 0.05) between changes in aortic SBP and Tr during CPT after L-citrulline supplementation. We conclude that oral L-citrulline supplementation attenuates the brachial SBP, aortic SBP, and aortic PP responses to CPT in young normotensive men. Increased wave reflection time contributes to the reduction in aortic SBP response to CPT.